I teach a class using Windows Multipoint Network 2011 with 12 clients.  

I reuse User1-12 email address for each class, but create a new Outlook account for each student with their own userid and password.  Once the outlook account is created, some users inboxes have old emails from the former student, even though

I've selected create a new file AND options to delete everything off the server after 14 days.  These accounts for in-class use are created usually 6-8 weeks after the previous account, so plenty of time for server to have deleted the old emails, even though I asked it to create a new file.

I can obviously delete the old emails, but this shouldn't be occurring.  Any suggestions?

First, please make sure if the mailbox database would be reset after the account is deleted. If not, that may cause the problem.

Since I'm not clear what type of accounts do you use in your network, I suggest you post this question in the following forum:

http://social.technet.microsoft.com/Forums/windowsserver/en-US/home?forum=windowsmultipointserver

Regards.